The disclosed embodiments generally pertain to a gas turbine engine. More particularly, but not by way of limitation, present embodiments relate to overspeed protection of gas turbine engines during malfunction conditions.
A typical gas turbine engine generally possesses a forward end and an aft end with its several core or propulsion components positioned axially therebetween. An air inlet or intake is at a forward end of the engine. Moving toward the aft end, in order, the intake is followed by a compressor, a combustion chamber, and a turbine. It will be readily apparent from those skilled in the art that additional components may also be included in the engine, such as, for example, low pressure and high pressure compressors, and high pressure and low pressure turbines. This, however, is not an exhaustive list. An engine also typically has an internal shaft axially disposed along a center longitudinal axis of the engine. The internal shaft is connected to both the turbine and the air compressor, such that the turbine provides a rotational input to the air compressor to drive the compressor blades.
In operation, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract gas energy from the combustion gases and converts such to mechanical energy. A high pressure turbine first receives the hot combustion gases from the combustor and includes a stator nozzle assembly directing the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a supporting rotor disk. In a two stage turbine, a second stage stator nozzle assembly is positioned downstream of the first stage blades followed in turn by a row of second stage rotor blades extending radially outwardly from a second supporting rotor disk.
In a malfunctioning condition, gas turbine engine fuel systems generally default to one of two conditions. In one condition, the engine fuel supply is shut off and the engine is shutdown with a fuel shutoff system. In a second condition, the engine fuel is supplied in a manner so that the engine is operated at high speed, at or near redline condition with a hydromechanical overspeed governor. Neither of these methods of controlling fuel flow or engine operating conditions is optimal.
As may be seen by the foregoing, it would be desirable to overcome these and other deficiencies with gas turbine engine components so that fuel flow may be controlled and normal engine operation maintained with failures in the normal fuel metering and head regulator systems.